1. Field of the Invention
The present invention relates to a shock absorber in which the dampening effects are regulated by control of the flow of an incompressible fluid through internal orifices by means of a compressible fluid in an internal cavity.
2. Description of the Prior Art
Shock absorbers have long been employed for use in automotive vehicles to dampen the effects of spring action in a vehicle during cornering and in traveling over uneven surfaces. Conventional shock absorbers employ a hollow cylinder and a piston on a piston rod that moves within the cylinder. The cylinder is filled with an incompressible fluid, such as hydraulic fluid. The piston is formed with one or more longitudinal orifices which permit the passage of the hydraulic fluid at a controlled flow rate governed by the orifice size and viscosity of the hydraulic fluid. Either the piston rod or the cylinder is connected to the vehicle chassis and the other member is connected to the vehicle passenger compartment frame.
When the vehicle turns sharply or travels over an uneven roadway, the piston will move reciprocally within the cylinder at a rate controlled by the viscosity of the fluid and the sizes of the orifices, as longitudinal movement of the piston relative to the cylinder can only occur when hydraulic fluid is displaced from the portion of the cylinder toward which the piston is moving. Hydraulic fluid is substantially incompressible and can only be displaced by the passage of the hydraulic fluid through the longitudinal orifices to the opposite side of the piston in the cylinder. The stiffness or vibration dampening characteristics of the shock absorber are thus uniform throughout the range of movement of the piston relative to the cylinder, since the sizes of the orifices is fixed and the viscosity of the hydraulic fluid does not vary significantly during operation of the shock absorber.